The first symptom of poisoning is a severe itching of the
skin. Later, a red inflammation and a blistering of the skin
occurs. In severe cases, oozing sores develop. The rash spreads
by the poisonous sap (urushiol), not as the result of contamination
from sores. The blood vessels develop gaps that leak fluid
through the skin, causing blisters and oozing. When you cool
the skin, the vessels constrict and don't leak as much according
to Robert Rietschel, M.D. Chairman of Dermatolgy at New Orleans'
Ochsner Clinic.

Symptoms
Most people develop symptoms 24-48 hours after contact. The interval
varies considerably, because of individual sensitivity and the
amount of sap contacting the skin. Healed areas often remain supersensitive
to further contact for several months.

The first symptom of poisoning is a severe itching of the skin.
Later, a red inflammation and a blistering of the skin occurs.
In severe cases, oozing sores develop. The rash spreads by the
poisonous sap, not as the result of contamination from sores.
Although extremely irritating, most cases disappear in a week
or 10 days. In the meantime, relief may be found through the application
of medication available in most drugstores. However, severe rashes,
especially those covering large areas or accompanied by above-normal
body temperatures, should be examined by a physician. Medical
treatment is most effective if applied before the oozing sores
appear.

Treatment

Wash infected skin as soon as possible with cold water to minimize
the severity of the rash and prevent the spread of the sap to
uninfected parts of the body. Unfortunately, your skin absorbs
the active compounds in the sap within the first 3 minutes, and
you cannot prevent the dermatitis without medical treatment. Soap
and water are superior to water alone in removing the sap, but
they also temporarily remove a natural protective layer that helps
keep the active compounds from being absorbed through the skin.

Prevention

The most common way to get a rash from a poisonous plant is
to come in contact with the plant oil. Once you have the rash
it cannot be spread to other parts of your body or to another
person by touching the blisters or the fluid. The rash is spread
by the plant oil on the hands, for example, wiping the forehead
with the hand.

Learn to recognize and avoid the plant. If you find the plant
growing in your yard, use gloves to pull it up by the roots, and
discard the plant carefully, then discard or wash the gloves.
When walking through wooded areas, wear long pants and long sleeves.

Brushing up against the plant's leaves seldom results in breaking
out in a rash because the plant's oil is not released unless the
stem or leaf surface is broken. However, if you are exposed to
the plant oil, wash the affected area with cold water as soon
as possible. Carefully remove all exposed clothing and wash it.
Wash off all camping and sporting gear as well, if there is a
chance that it has been contaminated.